javascript ASCII和Hex互转的实现方法

<script>var symbols = " !/"#$%&'()*+,-./0123456789:;<=>?@";var loAZ = "abcdefghijklmnopqrstuvwxyz";symbols+= loAZ.toUpperCase();symbols+= "[//]^_`";symbols+= loAZ;symbols+= "{|}~";//Hex to ASCIIfunction toAscii(str){  valueStr = str.toLowerCase();  var hex = "0123456789abcdef";  var text = "";  var i=0;  for( i=0; i<valueStr.length; i=i+2 )  {    var char1 = valueStr.charAt(i);    if ( char1 == ':' )    {      i++;      char1 = valueStr.charAt(i);    }    var char2 = valueStr.charAt(i+1);    var num1 = hex.indexOf(char1);    var num2 = hex.indexOf(char2);    var value = num1 << 4;    value = value | num2;    var valueInt = parseInt(value);    var symbolIndex = valueInt - 32;    var ch = '?';    if ( symbolIndex >= 0 && value <= 126 )    {      ch = symbols.charAt(symbolIndex)    }    text += ch;  }  return text;}//ASCII to Hexfunction toHex(str){  var valueStr = str;  var hexChars = "0123456789abcdef";  var text = "";  for( i=0; i<valueStr.length; i++ )  {    var oneChar = valueStr.charAt(i);    var asciiValue = symbols.indexOf(oneChar) + 32;    var index1 = asciiValue % 16;    var index2 = (asciiValue - index1)/16;    if ( text != "" ) text += ":";    text += hexChars.charAt(index2);    text += hexChars.charAt(index1);  }  return text;}</script>